In conveying of bulk material, it is sometimes necessary to negotiate a curve, such as a curve in a mine passage. Generally speaking, flat conveyor belts cannot negotiate a transverse curve because the two edges cannot accommodate the difference in length between the inside bend radius and the outside bend radius. Essentially what happens is that the inside edge collapses because the edge tension is not maintained due to the shortened radius. The load on the belting is spilled over this inside edge. The outer edge of the belt will tend to roll up over the conveyor belt pushing the material on the belt toward the inside edge thereby compounding the problem.
Previously, there have been attempts at making conveying systems with conveyor belts capable of passing around curves. In one prior art system, a chain-driven, multiple pan conveyor has rigid sides shaped to prevent side spillage of material and an underlying continuous belt that prevents the material from dropping through the clearances between the articulated pans. The fabricating costs of the pans and the underlying belt makes the system relatively expensive. The pans limit the conveying capacity for a given belt width and height. And, the interacting metal pans and the chain drive of the system generate excessive noise creating an unfavorable working condition.
Another approach that has been taken to the problem is to provide a belt having outer edges of reduced thickness with guide rollers engaging the edges to hold the edge along the outer transverse bend down and to partially collapse the inner edge as it goes around the inside transverse bend. This type of belt is subject to substantial wear, particularly along the edges that are inherently weak due to the reduced thickness. Also, the edges of the belt are subjected to substantial crushing pressure by the guide rollers, creating the tendency to cause premature wearing and fraying of the belt edges. This inevitably leads to the belt jumping out from between the rollers under periodic heavy loading conidtions, causing spillage and costly down time. Eventually the belt must be replaced. Also, because the edges of the belt are thin, an unusually large number of support rollers are required under the belt making the conveyor system very costly.